There are many commercially successful non-volatile memory products being used today, particularly in the form of small form factor cards, which employ flash EEPROM (Electrically Erasable and Programmable Read Only Memory) cells formed on one or more integrated circuit devices. Some of the commercially available card formats include CompactFlash (CF) cards, MultiMedia cards (MMC), Secure Digital (SD) cards, and personnel tags (P-Tag). Hosts that may incorporate or access non-volatile small form factor cards include personal computers, notebook computers, personal digital assistants (PDAs), various data communication devices, digital cameras, cellular telephones, portable audio players, automobile sound systems, and similar types of equipment. In some systems, a removable card does not include a controller and the host controls operation of the memory in the card. Examples of this type of memory system include Smart Media cards and xD cards. Thus, control of the memory may be achieved by software on a controller in the card or by control software in the host. Besides a memory card implementation, this type of memory can alternatively be embedded into various types of host systems. In both removable and embedded applications, host data may be stored in the memory according to a storage scheme implemented by memory controller software and/or hardware. The data stored within a card is accessed via an interface that is controlled by a program and, in some cases, security hardware or software.
The increase in storage density of non-volatile memory cards allows an ever-growing number of host applications to make use of the additional storage space. For example, the additional storage may be utilized for MP3 audio files, high-resolution images files, video files, and documents, and a variety of advanced cellular telephone services, such as storing Multimedia Messaging Service (MMS) object attachments, and providing full personal information management (PIM) functionality, such as e-mail contact lists and calendars. A variety of applications may therefore share access to the non-volatile storage device and access data or store and manage their own data. While each application may share the overall quantity of storage space in a non-volatile memory card, the bandwidth, power consumption, and file security requirements of each application may differ.
For example, handheld computing devices such as cellular telephones may provide content storage, perhaps in a removable non-volatile storage device, in order to increase the average revenue by generating more data exchanges on a mobile network. This content includes valuable data, which may be data owned by a party other than the one that manufactures or sells the non-volatile storage device. Therefore, the content in a non-volatile storage device may need to be protected from access by unauthorized users or applications. On the other hand, an application to take pictures with a cellular telephone camera may need to allow other applications to access the picture files stored in the non-volatile storage card. In another example, applications such as video players may require high-bandwidth, low-latency access to non-volatile storage. At the same time, other applications that share access to the non-volatile storage, such as telephone address books, may have less demanding bandwidth and latency requirements. As shown by these examples, the number of host applications accessing a non-volatile storage device is increasing, as are the quantity and types of data that can be stored in a non-volatile storage device. Further, the requirements of increasingly complex applications extend beyond the mere quantity of storage space required. For example, if a non-volatile storage card does not recognize or accommodate these differing application requirements, the security of the data stored on the card may be compromised, or bandwidth may be misallocated among the applications sharing access to the non-volatile storage card.